unwind tables for asm blocks

J.W. Jagersma jwjagersma@gmail.com
Fri Feb 28 22:03:00 GMT 2020


On 2020-02-28 22:04, Florian Weimer wrote:
> * J. W. Jagersma:
> 
>>         asm("call %0" :: "i" (throw_exc));
> 
> Calling functions from inline assembly is typically invalid for many
> other reasons.  For example, on x86-64, there is no way to express that
> the red zone is clobbered.
> 
> What is the actual issue you are trying to solve?
> 
> Thanks,
> Florian
> 

The call instruction is just a practical example. The problem I want to
address is that no exception handling information is generated at all
for asm statements. Other operations, eg. memory access, division, etc
could trap and throw an exception. The unwind tables should cover this.

There is a comment in stmt_could_throw_p (tree-eh.c) that states:

    /* The only statements that can throw an exception are assignments,
         conditionals, calls, resx, and asms.  */

Which leads me to believe that the current behaviour is a bug.



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